In this technical overview, design engineer Tom Paquet explains the critical engineering principles behind designing custom cables for robotic systems. Modern robotics in industrial automation and advanced medical devices demand cables capable of carrying power, sensitive signals, and high-speed data simultaneously while enduring complex, repetitive motions over hundreds of thousands or millions of operational cycles.
Robotic movement generally comprises three fundamental motions:
- Bending: Traditional back-and-forth angular flexing.
- Torsion: Rotational twisting around the longitudinal axis.
- Rolling: Continuous flexing along a track, such as in automated C-track carrier systems.
A key challenge in robotic cable design is navigating the tradeoff between flexibility and flex life. Flexibility describes tactile suppleness—how easily a cable bends, handles, and lies flat. However, internal micro-movements between conductors and insulations that create suppleness can generate internal friction, abrasion, and stress points. In contrast, flex life measures the number of dynamic movement cycles a cable withstands before failure.
To achieve extended flex life and prevent permanent plastic deformation, engineers specify high-tensile alloy conductors paired with hard, deformation-resistant primary dielectric polymers (such as fluoropolymers and polyesters). For outer jackets, polyurethane (TPU) is preferred for its exceptional abrasion resistance, mechanical toughness, and ability to bind internal components firmly in place. Furthermore, because bulky power conductors and fragile data pairs experience uneven physical stress, careful geometric layout, low-stress positioning, and sufficient internal cross-sectional space are vital to maximizing cable lifespan.
Key Technical Takeaways
- Three Modes of Robotic Motion: Robotic cables must be engineered to withstand bending, torsional rotation, and rolling C-track flexing.
- Flexibility vs. Flex Life: Tactile flexibility can create internal friction and wear; flex life prioritizes long-term mechanical survival across millions of cycles.
- Alloy Conductors: High-strength copper alloys resist permanent plastic deformation far better than standard soft copper conductors.
- Insulation & Jacketing: Hard fluoropolymer and polyester primaries resist mechanical crushing, while polyurethane jackets provide abrasion defense and structural integrity.
- Layout & Internal Spacing: Strategic placement of delicate data pairs away from heavy power conductors—along with adequate internal spacing—prevents premature fatigue.
- Validation Testing: Specialized testing rigs evaluate torsional stress, rolling flex, and multi-axis bending to corroborate real-world longevity.
Robotic Cable Design Transcript
Welcome and Robotic Performance Requirements
Hi, I’m Tom Paquet. I’m a Design Engineer here at New England Wire Technologies. We receive all kinds of questions during the design process, and today I’m going to answer some of those for you.
What kind of cable performance requirements do you typically see for robotics applications?
We see all kinds of requirements. Robotics is not just motors. It’s signal, it’s data. At this point, robots have become more and more complex, performing more and more tasks. So we could basically see anything. It also comes down to what sort of environment it’s going to be living in, whether it’s a medical application or an industrial application; these are all important things for us to consider.
The Three Modes of Robotic Motion
Can you explain the difference in the flexing movements required for robotics?
So robots move in very dynamic and complex ways, but generally they boil down to three main types of motion:
- The first one is just bending, very traditional.
- Then there’s torsional, which is rotational.
- And then we also see like C-track applications; you might see something that we call rolling.
Pretty much all robotic motions are made up of those three types of motion.
Flexibility vs. Flex Life: Elastic and Plastic Deformation
So what is the difference between flexibility and flex life?
Flexibility is how easily a cable moves, how flat it lies on a surface, how limp or dead it is. You know, it’s basically how the cable feels. All of these things are a tradeoff in a robotics application, though. All of those things that contribute to your flexibility are also things that can eventually sabotage your cable in the long run. All that flexibility comes from micro-movements within your cable between the conductors and the insulation systems, and those can result in stress points and eventually failures. Or they can cause friction and abrasion, which will also result in failures.
Flex life, on the other hand, is generally given in terms of cycles. So how many times can you bend something back and forth—that back-and-forth motion is called a cycle. Most cables last a few hundred or maybe a few thousand cycles, depending on how rigorous the application. For robotics, it is really, really critical that we be able to last hundreds of thousands or even millions of cycles. So it’s a real fine balance that we need to meet between the flexibility and the flex life.
Material Selection: Alloys and Tough Polymers
What are the special material considerations for good flex life cables?
So this is kind of a two-part answer. The first one is conductor; the second one is the insulation system.
From a conductor standpoint, we’re pretty much always going to be looking at alloys. Alloys are harder than copper. This provides a big advantage because they’re less likely to deform plastically. Not to dive into metallurgy 101 too much, but all materials deform elastically and then plastically. If you bend something and it returns to its original shape, that’s an elastic deformation. If you bend it and then it keeps its new shape, that’s a plastic deformation. Basically, that’s just damage to the cable at this point. So we’re looking to avoid that. Alloys offer a nice hard material that is less likely to produce these defects.
The second part of that question is the insulation system. What this boils down to is choosing plastics that are going to last a really long time. Like with the conductors, these plastics need to be resistant to this plastic deformation. So we tend to choose very hard plastics. Primary insulations would be things like fluoropolymers or polyester. And we would use an outer insulation system, which is generally a urethane because it provides excellent abrasion resistance and it also tends to hold all of those inner components nice and tightly together.
Geometric Cable Design and Internal Spacing
Why is cable design and layout so important?
Like we talked about earlier, there are a lot of different types of components that can be put in these cables. Obviously there’s power, there’s data, and signal. All these different components generally aren’t the same size and shape. And so it’s important how you put those things together to ensure that they last as long as possible. Power conductors tend to be a lot larger and so more robust. The smaller data pairs tend to be a little more fragile, and so it’s important that we work to fortify those and put them in low-stress positions.
Generally, part of fortifying a cable is making it larger. So if including a cable into your design is like the last thing that you come to the table with, it’s important to remember to leave a lot of space, because the larger this cable is, the longer we can make it last.
Mechanical Testing for Robotic Applications
Does NEWT provide testing for robotics cables?
We do. We offer a battery of testing. We offer bending endurance, torsional stress testing, rolling torsional testing, and we’re always willing to work with customers to develop new testing. Testing for robotics cables is very important because it can give you real-life data to corroborate that this cable is going to perform the way that you hope it does.
Aesthetic Design in Medical and Consumer Robotics
Are aesthetics important for robotics cables?
Aesthetics are always important for cables, especially when the customer gets to see the cable—any sort of exposed cable. In the medical industry, this might look like a nice glossy, light-colored cable. They’re easy to clean. People always want to be able to see that something is clean in the medical industry, so the cable should represent that as well. If you’re dealing with something that might be a little more like for kids, you might want something that’s a little more vibrant, a little more colorful. And we have all sorts of color matching on-site, so we can give you pretty much anything you want.
If you’ve got any more questions, anything that I didn’t touch on or talk about today, feel free to reach out to us at newenglandwire.com.